Adaptive inductive power supply

ABSTRACT

A contactless power supply has a dynamically configurable tank circuit powered by an inverter. The contactless power supply is inductively coupled to one or more loads. The inverter is connected to a DC power source. When loads are added or removed from the system, the contactless power supply is capable of modifying the resonant frequency of the tank circuit, the inverter frequency, the inverter duty cycle or the rail voltage of the DC power source.

This application incorporates by reference the following references:U.S. Pat. No. 7,522,878 to Baarman, which is entitled “AdaptiveInductive Power Supply with Communication” and issued Apr. 21, 2009;U.S. Pat. No. 7,132,918 to Baarman et al., which is entitled “InductiveCoil Assembly” and issued Nov. 7, 2006; U.S. application Ser. No.10/689,154 to Baarman, which is entitled “Electrostatic Charge StorageAssembly” and filed on Oct. 20, 2003; and U.S. Pat. No. 7,518,267 toBaarman, which is entitled “Adapter” and issued Apr. 14, 2009.

BACKGROUND OF THE INVENTION

This invention relates generally to contactless power supplies, and morespecifically to inductively coupled contactless power supplies.

Contactless energy transmission systems (CEETS) transfers electricalenergy from one device to another without any mechanical connection.Because there is no mechanical connection, CEETS have many advantagesover conventional energy systems. They are generally safer because thereis little danger of sparks or electric shocks due to the isolation ofthe power supply. They also tend to have a longer life since there areno contacts to become worn. Due to these advantages, CEETS have beenused in everything from toothbrushes to portable telephones to trains.

CEETS are composed of power supplies and remote devices. The remotedevices could be chargeable, such as batteries, micro-capacitors, or anyother chargeable energy source. Alternatively, CEETS could directlypower the devices.

One kind of CEETS uses magnetic induction to transfer energy. Energyfrom a primary winding in the power supply is transferred inductively toa secondary winding in the chargeable device. Because the secondarywinding is physically spaced from the primary winding, the inductivecoupling occurs through the air.

Without a physical connection between the primary winding and thesecondary winding, conventional feedback control is not present. Thus,control of the energy transfer in a CEETS from the primary to thesecondary is difficult.

One common solution is to design a CEETS dedicated to one type ofdevice. For example, a CEETS for a rechargeable toothbrush is designedonly for recharging a toothbrush, while a CEETS for a rechargeabletelephone works only with a specific type of telephone. While thissolution allows the CEET to operate effectively with one particulardevice, it fails to be sufficiently flexible to allow the power supplyto operate with different rechargeable devices.

Obviously, making a CEETS for each specific chargeable device is costlyand inefficient. Thus, a system for contactless energy transmissionwhich is efficient and can be used with a large variety of devices ishighly desirable.

SUMMARY OF THE INVENTION

The aforementioned problems are overcome in the present invention.

A contactless power supply inductively couples by way of a tank circuitto a device. The power supply has a controller for dynamically adjustingthe resonant frequency of the tank circuit. The tank circuit could haveeither a variable capacitor or a variable inductor, or both. In oneembodiment, the power supply also may have an inverter. A drive circuitconnected to the inverter controls the frequency of the inverter and theduty cycle of the inverter. A controller with an attached memory directsthe operation of the inverter by way of the drive circuit.Alternatively, The inverter may also be connected to a DC power source.The controller could then change the rail voltage of the DC powersource.

By altering the resonant frequency of the tank circuit, the frequency ofthe inverter, the duty cycle of the inverter and the rail voltage of thepower supply, the contactless power supply can energize a variety ofdifferent devices. The power supply can even energize several differentdevices at the same time. This ability to power a multitude of differentdevices overcomes many of the limitations previously associated withCEETS. Further, because the power supply can energize a variety ofdifferent devices, a central single source for supply power to a varietyof small electronic devices is possible.

In one embodiment, a sensor may also coupled to the tank circuit. Itwould monitor various operational characteristics of the tank circuit,such as the phase of the current within the tank circuit. Theseoperation characteristics are indicative of the total load energized bythe power supply. When the operational characteristics indicate that thepower supply is not efficiently supplying power to the load, thecontroller causes the power supply to seek an improved configuration.

The process of seeking an improved configuration may include one or moreof the following steps. The power supply could automatically attempt tocompensate by changing the frequency of the inverter and the duty cycleof the inverter. If this sufficiently correct the efficiency of thepower supply, the controller causes the tank circuit to change itsresonant frequency. As is well known, the resonant frequency of a tankcircuit is in fact a range centered about a frequency. The tank circuitwill resonate at frequencies which are approximately the resonantfrequency. However, the adaptive power supply described hereinreconfigures the tank circuit to have a substantially different resonantfrequency.

The tank circuit may consist of either a variable inductor or a variablecapacitor or both. The controller would then change the inductance ofthe variable inductor or the capacitance of the variable capacitor, orboth, thus causing the tank circuit to have a different resonantfrequency.

The controller may also establish a new rail voltage for the DC powersource. It also sets a new inverter frequency and a new duty cycle forthe inverter. The adaptive power supply then operates with the newconfiguration.

If the adaptive power supply is still not operating effectively, thepower supply will once again attempt to rectify the problem by changingthe frequency of the inverter and the duty cycle of the inverter. If theproblem is still not corrected, then the power supply will repeat theprocess of reconfiguring the tank circuit, setting a new inverterfrequency and setting a new duty cycle.

This power supply continually searches for the most efficient settingsto deliver power to the devices. However, if none of the varioussettings delivers power efficiently to the devices, then the powersupply will select the most efficient of the previous configurations andoperate the power supply with those settings.

Thus, the power supply efficiently powers a variety of loads. Further,because the power supply is contactless, a user does not need to have amultitude of different power supplies or connectors.

These and other objects, advantages and features of the invention willbe more readily understood and appreciated by reference to the detaileddescription of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an adaptive inductive ballast in accordancewith one embodiment of the present invention.

FIG. 2 is a schematic diagram of the resonance-seeking ballast of theattached patent application marked to show changes to incorporate theadaptive inductive ballast of the present invention.

FIG. 3 is a flow chart illustrating operation of the adaptive inductiveballast.

FIG. 4 is a block diagram for an adaptive contactless energytransmission system.

FIGS. 5A and 5B are a flow chart showing the operating of an adaptivecontactless energy transmission system.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention provides an adaptive inductive ballast circuit inwhich the inductance and/or the capacitance of the power supply circuitis variable to provide a broad range of adaptability, thereby permittingthe ballast circuit to power a variety of inductively powered deviceswith widely differing load characteristics. For purposes of disclosure,the present invention is described in connection with aresonance-seeking ballast circuit, and more particularly in connectionwith the inductive ballast described in U.S. patent application Ser. No.10/246,155 entitled “Inductively Coupled Ballast Circuit,” whichincorporated by reference into this application in its entirety. Thepresent invention is, however, well suited for use with other inductiveballast circuits.

A block diagram showing the general construction of an adaptiveinductive ballast 10 in accordance with one embodiment of the presentinvention is shown in FIG. 1. As illustrated, the adaptive inductiveballast 10 generally includes a microprocessor 12 that controlsoperation of the circuit, a multi-tap primary 14 for generating amagnetic field, a wave shaper and drive subcircuit 16 that generates thesignal applied to the primary 14, a current sense subcircuit 18 thatmonitors the signal applied to the primary 14 and provides correspondingfeedback to the microprocessor 12, a capacitance switch 20 for adjustingthe capacitance values in the wave shaper and drive subcircuit 16, andan inductance switch 22 for adjusting the inductance of the multi-tapprimary 14. The microprocessor is a conventional microprocessor widelyavailable from a variety of suppliers.

The capacitance switch 20 generally includes two banks of capacitors anda plurality of switches, such as transistors, that are selectivelyactuatable by the microprocessor 12 to control the values of the twocapacitor banks. The capacitors in each bank can be arranged in seriesor parallel depending on the desired range and distribution of possiblecapacitance values. The first bank of capacitors replace capacitor 271of the pre-existing resonance-seeking ballast shown in the abovereferenced application. Similarly, the second back of capacitors replacecapacitor 272 of the pre-existing resonance-seeking ballast shown in theabove referenced patent application. In effect, the capacitance switch20 makes capacitors 271 and 272 from the pre-existing resonance-seekingballast into variable capacitors, the values of which are controlled bythe microprocessor 12. Alternatively, the described capacitance switch20 can be replaced by other circuitry capable of providing variablecapacitance.

The inductance switch 22 generally includes a multi-tap primary 14 and aplurality of switches, such as transistors, that are selectivelyactuatable by the microprocessor 12 to control the values of theinductance of the primary 14. The multi-tap primary 14 replaces primary270 of the pre-existing resonance-seeking ballast shown in the attachedpatent application. In effect, the inductance switch 22 makes primary270 from the pre-existing resonance-seeking ballast into a variableinductance coil by varying the number of turns in the primary 14, thevalue of which is controlled by the microprocessor 12. Alternatively,the described inductance switch 22 can be replaced by other circuitrycapable of providing variable inductance.

In general operation, the microprocessor 12 is programmed to receiveinput from the current sense subcircuit 18, which is indicative of thecurrent applied to the primary 14. The microprocessor 12 is programmedto separately adjust the capacitance switch 20 and the inductance switch22 to cycle through the range of capacitance values and inductancevalues available to the circuit. The microprocessor 12 continues tomonitor the input from the current sense circuit 18 while adjusting thecapacitance and inductance values to determine which values provideoptimum current to the primary 14. The microprocessor 12 then locks theadaptive ballast into the optimum settings.

Some of the changes required to adapt the resonance-seeking inductiveballast of the application patent application into an embodiment of theadaptive inductive ballast circuit 10 are noted in the schematic diagramof FIG. 2.

While the pre-existing resonance-seeking ballast is described in greaterdetail in U.S. patent application Ser. No. 10/246,155, an overview ofthe circuit may be helpful to a fuller understanding of this invention.A ballast feedback circuit is connected at point A and a control circuitis connected at point B. Oscillator 144 provides half bridge inverter148 with an alternating signal by way of drive 146. Half bridge inverterpowers tank circuit 150. Current sensing circuit 218 provides feedbackto oscillator 144. The feedback circuit, control circuit, oscillator,half bridge inverter, drive and current sensing circuit 218 as well asother supporting circuitry is more fully described in the abovereferenced patent application.

In FIG. 2, a phase delay could be inserted at E and can be controlled asa delay line or even DSP (Digital Signal Processing) could be used todelay this signal. This delay can be used to throttle the phase andcontrol secondary amplitude. At F, switched capacitance can adjust theresonant frequency based on the adjustable primary inductance. Simpletransistors can be used to switch in and out capacitance. Thecapacitance is changed when the primary inductor changes as to matchload. At G, primary inductance can be switched to adjust the powerrequired by the secondary circuit. With that load information, thecontrol processor can adjust the inductance as needed to provide thepower required. The inductance can be switched using transistors andmultiple taps from the primary inductor controlled by themicroprocessor.

The operating sequence of the adaptive inductive ballast circuit isdescribed in more detail in connection with FIG. 3. In operation, theillustrated system waits until it determines that a load is presentbefore applying power to the primary 14. This will save power and may bedone by providing each inductively powered device with a magnet thatactuates a reed switch adjacent to the primary. Alternatively, auser-actuated switch (not shown) may be provided so that the user canengage the power supply when an inductively powered device is present.As another alternative, the inductively powered device may be configuredto mechanically actuate a switch when it is placed into located by theprimary to signal its presence. As a further alternative, the switchingmechanism can be eliminated and the ballast circuit can provide power tothe primary 14 regardless of the presence of a load.

Once the power supply circuit is activated, the circuit adjusts itsfrequency to optimize the current applied to the primary. After theappropriate operating frequency has been determined at initialcapacitance and inductance values, the microprocessor locks the ballastcircuit into the operating frequency and then begins to cycle throughthe range of inductance values available through the multi-tap primary.After each change in inductance value, the microprocessor unlocks theoperating frequency and permits the ballast circuit to seek resonance,settling at a frequency that provides optimal current to the primary.The microprocessor continues cycling through the available inductancevalues until it has determined which value provides optimal current tothe primary. In one embodiment, a progressive scanning process is usedto determine the appropriate inductance value. This is achieved bystarting the scanning process with the lowest inductance value, andsequentially stepping up the inductance value until the change ininductance value results in a reduction in the current applied to theprimary. The microprocessor will then step back down one inductancevalue, where the greatest current was achieved. Alternatively, thescanning process may begin with the highest inductance value, andsequentially step down the inductance value until the change ininductance value results in a reduction in the current applied to theprimary. The microprocessor will then step back up one inductance value,where the greatest current was achieved. As another alternative, themicroprocessor can step through each inductance value to determine thecorresponding current, and after stepping through each value, return tothe inductance value that provided the greatest current to the primary.

After the appropriate inductance value is determined, the microprocessorlocks the circuit at the determined inductance value and begins to cyclethrough the capacitance values. In one embodiment, the microprocessoruses a progressive scanning technique to determine the capacitance thatprovides the primary with the greatest current. The scanning process mayprogress upwardly from the lowest capacitance value or downwardly fromthe highest capacitance value, as described above in connection with thescanning process for the inductance value. As an alternative to aprogressive scanning process, the microprocessor can step through eachcapacitance value to determine the corresponding current, and afterstepping through each value, return to the capacitance value thatprovided the greatest current to the primary.

In this embodiment, the frequency of the ballast circuit is notpermitted to vary once the appropriate inductance value has beendetermined. The microprocessor can, alternatively, be programmed topermit the ballast circuit to seek resonance after each change incapacitance value.

In an alternative embodiment, the microprocessor may be programmed toprovide adjustment of only the capacitance value or only the inductancevalue of the power supply circuit. In the former alternative, themulti-tap primary can be replaced by a conventional single-tap primaryand the inductance switch can be eliminated. In the latter alternative,the capacitor bank can be replaced by a single set of capacitors and thecapacitance switch can be eliminated. In another alternative embodiment,the microprocessor can be programmed to adjust the capacitance beforeadjusting the inductance.

As noted above, the present invention is not limited to use inconnection with a resonance-seeking ballast. In other applications, acurrent sensor may be incorporated into the ballast to provide input tothe microprocessor that is representative of the current being appliedto the primary. In operation without a resonance-seeking ballast, themicroprocessor will separately cycle through the various capacitance andinductance values to determine the values that provide optimum power tothe primary.

In a further alternative embodiment, the adaptive inductive ballast 10may include phase delay circuitry (not shown) that permits the ballast10 to throttle the phase and control secondary amplitude. The phasedelay circuitry may include a delay line or a Digital Signal Processor(DSP) that is connected to the wave shaper and drive circuit 16following the operational amplifier 210.

Further exemplifying the ideas and concepts expressed above, anadditional embodiment for an adaptive contactless energy transmissionsystem is shown in the block diagram of FIG. 4. The adaptive contactlessenergy transmission system is comprised of adaptive inductive powersupply 305 and remote device 307.

As is well know, power source 310 is a DC power source providing DC(direct current) power to inverter 312. Inverter 312 converts the DCpower to AC (alternating current) power. Inverter 312 acts as an ACpower source supplying the AC power to tank circuit 314. Tank circuit314 is inductively coupled to secondary winding 316 of remote device307.

Secondary winding 316 of remote device 307 has no core. Line 322indicates an air gap between remote device 307 and adaptive inductivepower supply 305.

Remote device 307 has a load 320. Load 320 could include a rechargeabledevice, such as a micro-capacitor or a rechargeable battery.Alternatively, load 320 could be a lamp, radio or any other electricaldevice adapted to receive power from adaptive inductive power supply 305whenever remote device 307 is placed in proximity of adaptive inductivepower supply 305.

Circuit sensor 324 is coupled to the tank circuit 314 and inverter 312.Circuit sensor 324 is also coupled to controller 326. Circuit sensor 324provides information regarding the operational parameters of adaptiveinductive power supply 305. For example, circuit sensor 324 could be acurrent sensor used to provide controller 326 information regarding thephase, frequency and amplitude of the current in tank circuit 314.

Controller 326 could be any one of a multitude of commonly availablemicrocontrollers programmed to perform the functions hereinafterdescribed, such as the Intel 8051 or the Motorola 6811, or any of themany variants of those microcontrollers. Controller 326 could have a ROM(read only memory) and RAM (random access memory) on the chip.Controller 326 could have a series of analog and digital outputs forcontrolling the various functions within the adaptive inductive powersupply.

Controller 326 is connected to memory 327. Controller 326 is alsocoupled to drive circuit 328. Drive circuit 328 regulates the operationof inverter 312, such as the frequency and timing of inverter 312. Drivecircuit 328 could be constructed in a number of different manners. Forexample, driver circuit 328 could be constructed of discrete componentssuch as transistors, resistors and capacitors; it could be a discreteintegrated circuit designed to drive inverters; or it could be afunctional component of controller 326 if controller 326 were amicrocontroller.

Controller 326 is also coupled to power source 310. Controller 326 canmanipulate the rail voltage of power source 310. As is well known, byaltering the rail voltage of power source 310, the amplitude of theoutput of inverter 312 is also altered.

Finally, controller 326 is coupled to variable inductor 330 and variablecapacitor 332 of tank circuit 314. Controller 326 could be amicrocontroller, such as an 8051-type microcontroller. Alternatively,controller 326 could be a microprocessor with additional supportingcircuitry.

Controller 326 can modify the inductance of variable inductor 330 or thecapacitance of variable capacitor 332. This could be done, e.g., byswitching in or out additional capacitor or inductors or by changing thephysical characteristics of variable inductor 330 or variable capacitor332. By modifying the inductance of variable inductor 330 and thecapacitance of variable capacitor 332, the resonant frequency of tankcircuit 314 can be changed.

By modifying the inductance of variable inductor 330 or the capacitanceof variable capacitor 332, or both, tank circuit 314 may have a firstresonant frequency and a second resonant frequency. Tank circuit 314could also have several resonant frequencies. As used herein, the term“resonant frequency” refers to a band of frequencies within which tankcircuit 314 will resonate. As is well known, a tank circuit will have aresonant frequency, but will continue to resonate within a range offrequencies.

Variable inductor 330 could be a thyristor controlled variable inductor,a compressible variable inductor, parallel laminated core variableinductor, a series of inductors and switches capable of placing selectfixed inductors into tank circuit 314, or any other controllablevariable inductor. Variable capacitor 332 could be a switched capacitorarray, a series of fixed capacitors and switches capable of placingselect fixed capacitors into tank circuit 314, or any other controllablevariable capacitor.

Tank circuit 314 also includes primary winding 334. Primary winding 334and variable inductor 330 are shown separate. Alternatively, primarywinding 334 and variable inductor 330 could be combined into a singleelement.

Tank circuit 314 is shown as a series resonant tank circuit. A parallelresonant tank circuit could also be used.

FIGS. 5A and 5B show a flow chart showing the operation of adaptiveinductive power supply 305 of adaptive contactless energy transmissionsystem shown in FIG. 4.

When turned on (step 400), controller 326 initializes the resonantfrequency of tank circuit 314 by setting the inductance of variableinductor 330 and the capacitance variable capacitor 332 so that tankcircuit 314 operates at a pre-selected initial resonant frequency. Step402. Controller 326 initializes drive circuit 328 to operate at apre-selected frequency with a pre-selected phase offset. Controller 326initializes power source 310 to operate at a predetermined rail voltage.Step 402.

In order to conserve power, when adaptive inductive power supply 305 isinitially energized, adaptive inductive power supply 305 might beinitialized to supply power at a very low level. Alternatively, adaptiveinductive power supply 305 might be initialized to supply power at amore moderate level to accommodate some common remote devices.

Controller 326 then sets the nominal range for the operating parameters.Step 404. The operating parameters for the power supply are variousmeasures of current and voltage throughout the system. For example, thepeak to peak inverter voltage, the RMS current flowing through theprimary winding, and the phase offset of the current flowing through theprimary winding are all operating parameters. For example, the operatingrange could include a range of the phase offset between the invertervoltage and the voltage current, a range for the current amplitude, anda range for the inverter output voltage. As a further example, anoperating range could be an inverter voltage from 5 Volts to 5.3 volts,with a current phase offset of no more than 20 degrees, and a currentamplitude of between ½ and 1 amp.

The nominal range is the acceptable range of possible values for theoperating parameters. If an operating parameter are not within thenominal range, then the power supply is not operating efficiently.

Returning to FIG. 5, the system then idles. Step 406. Controller 326continually monitors the operating parameters of adaptive inductivepower supply 305. If the operating parameters fall within the nominalrange, then the circuit continues to idle. Step 408.

When remote device 307 is placed near primary winding 334, then power isdrawn from adaptive inductive power supply 305. As a result, theoperating parameters change. If the operating parameters fall outside ofthe nominal range, then controller 326 reconfigures adaptive inductivepower supply 305.

If adaptive inductive power supply 305 had an initially low powersetting, adaptive inductive power supply 305 would thus sense thepresence of the remote device, and automatically increase power to amore moderate level.

Obviously, reconfiguration of adaptive inductive power supply 305 couldbe triggered by one operating parameter falling outside of the nominalrange, or reconfiguration of adaptive inductive power supply 305 couldbe triggered by a combination of operating parameters falling outside ofthe nominal range. It is satisfactory to monitor only the phase of thecurrent flowing through the primary winding. However, variousenhancements where other operating parameters are measured and weightedtogether could be readily conceived.

First, controller 326 causes drive circuit 328 to alter the duty cycleof inverter 312. Step 410. The duty cycle of inverter 312 is altered,and the altered duty cycle is stored in memory 327.

The operating parameters are again measured. Step 412. If the operatingparameters are still outside of the nominal range, then a ‘best knownsetting’ flag is checked. Step 414. The ‘best known setting’ flag isdiscussed below.

If the “best know setting flag” is not set, then controller 326determines whether the inverter frequency can be adjusted and stillmaintain resonance within tank circuit 314. Step 418. Controller 326first finds the maximum and minimum resonant frequency of tank circuit314.

The maximum and minimum resonant frequency of tank circuit 314 for anyparticular configuration of variable inductor 330 and variable capacitor332 could be stored in memory 327. In the alternative, the maximum andminimum resonant frequency of tank circuit 314 could be calculated fromthe inductance of primary winding 334, the inductance of variableinductor 330, and the capacitance of variable capacitor 332. Controller326 then compares the maximum and minimum resonant frequency of tankcircuit 314 with the current operating frequency of inverter 312.

If possible, then controller 326 causes drive circuit 328 to adjust theinverter frequency and stores the new inverter frequency in memory 327.Step 420. The circuit returns to the idle state. Step 406. If theinverter frequency cannot be adjusted within the resonant frequency ofthe current configuration of tank circuit 314, then controller 326determines whether the configuration of tank circuit 314 can bemodified. Step 422.

If it can be modified, then controller 326 stores the current frequency,duty cycle, rail voltage, tank circuit configuration, and operatingparameters in memory 327. Step 424. It then adjust the tank circuitresonant frequency. Step 426. Adjustment of the tank circuit resonantfrequency is accomplished by changing the inductance of variableinductor 330 and the capacitance of variable capacitor 332.

The rail voltage could then be changed. Step 428. Since the resonantfrequency of tank circuit 314 has been altered, a new nominal range forthe operating parameters is calculated or loaded from memory 327. Step430. The power supply then returns to idle. Step 406.

If the configuration of tank circuit 314 can not be further modified,then controller 326 searches for the best prior configuration. Step 432.Controller 326 compares the operating parameters previously stored andselects the best configuration.

After selecting the best configuration, controller 326 retrieves varioussettings of adaptive inductive power supply 305 from memory for thatconfiguration. Step 433. Controller 326 then sets the configuration oftank circuit 314 by setting the inductance of adjustable inductor 30 andcapacitance of adjustable capacitor 32. Step 434. Controller 326 thensets the frequency of inverter 312. Step 436. Controller 326 then setsthe duty cycle of inverter 312. Step 438. Controller 326 sets the railvoltage of power source 310. Step 440.

Controller 326 then stores the expected operating parameters in memory327. Step 442. Alternatively, controller 326 could set a pointer to theexpecting operating parameters in memory 327. Controller 326 then setsthe ‘best known setting’ flag. Step 444. The power supply then returnsto the idle state. Step 406. The ‘best known setting’ flag is anindication to controller 326 that the current settings being used byadaptive inductive power supply 305 are the best available.

If the ‘best known setting’ flag is set, then the system is operating atits best settings even though the operating parameters are outside ofthe nominal range. Further changes to the inverter frequency, resonantcircuit frequency, inverter duty cycle or rail voltage thus would notresult in any improvement to the system. With the ‘best known setting’flag set, the system checks if the operating parameters areapproximately equal to the expected operating parameters.

Thus, if the best known setting flag is set (See Step 414), controller326 checks whether the current operating parameters are approximatelythe same as the expected operating parameters. Step 446. If so, thenfurther adjustments to power supply will not result in any improvedperformance, and therefore the system merely returns to the idle state.Step 406.

If, on the other hand, the current operating parameters are notapproximately equal to the expected operating parameters, then the bestknown setting flag is cleared. Step 448. The process of reconfiguringadaptive inductive power supply 305 continues. Step 422.

The adaptive contactless energy transmission system described thus candynamically handle a variety of different devices. Adaptive inductivepower supply 305 automatically adjusts to different devices withdifferent loads, and continually determines and optimal operatingconfiguration for the power supply.

Further, more than a single device can be simultaneously powered byadaptive inductive power supply 305. As new devices are placed nearadaptive inductive power supply 305, controller 326 continually adjuststhe operating parameters of adaptive inductive power supply 305 tomaintain efficiency. This allows for one single power supply to providepower to a multitude of different devices. The devices need not belocated immediately adjacent adaptive inductive power supply 305. Thatcan be spaced at different distances away from adaptive inductive powersupply 305. For example, it is possible to construct a power supplywhereby sealed lights are stacked near adaptive inductive power supply305 and each light will be illuminated even though the distance fromadaptive inductive power supply 305 is different for each light.

The above description is of the preferred embodiment. Variousalterations and changes can be made without departing from the spiritand broader aspects of the invention as defined in the appended claims,which are to be interpreted in accordance with the principles of patentlaw including the doctrine of equivalents. Any references to claimelements in the singular, for example, using the articles “a,” “an,”“the,” or “said,” is not to be construed as limiting the element to thesingular.

The invention claimed is:
 1. A method for controlling operation of aninductive power supply system, the inductive power system including aninductive power supply having a controller and a tank circuit, the tankcircuit being driven by a drive circuit at a variable operatingfrequency to transfer power inductively to a remote device, the methodcomprising the steps of: establishing an inductive coupling between theinductive power supply and the remote device, wherein the remote deviceincludes a secondary inductor in electrical communication with a load;adaptively adjusting a variable impedance element of the inductive powersupply to adjust a resonant frequency of the tank circuit such that theresonant frequency is at or near the variable operating frequency,wherein said adaptive adjusting occurs while the remote device isinductively coupled with the inductive power supply; and adjusting thevariable operating frequency of the inductive power supply, whereinadjusting the variable operating frequency of the inductive power supplyincludes adjusting an operating parameter of the inductive power supplywith the controller, wherein said adjusting the variable operatingfrequency occurs while the remote device is inductively coupled with theinductive power supply.
 2. The method of claim 1 wherein said adjustinga variable impedance element includes adjusting with the controller atleast one of a variable capacitance or a variable inductance of the tankcircuit.
 3. The method of claim 1 further comprising adjusting a powerlevel of the inductive power supply.
 4. The method of claim 1 furthercomprising establishing an inductive coupling between the inductivepower supply and a plurality of remote devices having a secondaryinductor.
 5. The method of claim 1 wherein said adjusting an operatingfrequency includes adjusting the operating frequency in response to afeedback signal.
 6. The method of claim 1 further comprising repeatingsaid step of actively adjusting at least one of an operating frequencyof the inductive power supply.
 7. The method of claim 1 furthercomprising detecting an operational parameter of the tank circuit; anddetermining whether the operational parameter of the tank circuit in theinductive power supply is within a nominal range, wherein said adjustingis in response to determining that the operational parameter is notwithin the nominal range.
 8. The method of claim 1 further comprisingrepeating the step of adjusting the variable impedance element to adjustthe resonant frequency of the tank circuit to be at or near the variableoperating frequency.
 9. An inductive power supply for supplying power toa remote device, wherein the remote device includes a secondary inelectrical communication with a load, said inductive power supplycomprising: a primary configured to wirelessly couple with the secondaryof the remote device to transfer power to the remote device; drivecircuitry configured to drive the primary at an operating frequency,said operating frequency being variable; a variable impedance elementoperatively coupled to the primary, said variable impedance elementcapable of affecting a resonant frequency of said primary; a controlleroperatively coupled to said drive circuitry, said variable impedanceelement, and said primary, said controller programmed to: adaptivelyadjust said variable impedance element of said inductive power supply toadjust said resonant frequency of said primary such that said resonantfrequency is at or near said operating frequency, wherein saidcontroller is programmed to adaptively adjust said variable impedanceelement while the secondary of the remote device is wirelessly coupledwith said inductive power supply; and adjust said operating frequency ofsaid inductive power supply while the secondary of the remote device iswirelessly coupled with said inductive power supply such that saidoperating frequency is capable of varying during operation.
 10. Theinductive power supply of claim 9 further including a tank circuithaving said primary, and wherein said variable impedance element is atleast one of a variable capacitance or a variable inductance of saidtank circuit.
 11. The inductive power supply of claim 9 wherein saidcontroller is programmed to adjust a power level of said inductive powersupply.
 12. The inductive power supply of claim 9 wherein said inductivepower supply supplies power to a plurality of remote devices.
 13. Theinductive power supply of claim 9 wherein said controller is programmedto adjust said operating frequency in response to a feedback signal. 14.The inductive power supply of claim 9 wherein said controller isprogrammed to repeatedly adjust said operating frequency of saidinductive power supply.
 15. The inductive power supply of claim 9wherein said controller is programmed to: detect an operationalparameter of said primary; and determine whether said operationalparameter of said primary in said inductive power supply is within anominal range, wherein said operating frequency is adjusted in responseto a determination that said operational parameter is not within saidnominal range.
 16. The inductive power supply of claim 9 wherein saidcontroller is programmed to repeatedly adjust the variable impedanceelement to adjust the resonant frequency to be at or near the variableoperating frequency.